1. Field of Invention
This invention relates to article storage and handling systems for retrieving articles from a storage rack and transferring the articles to a collecting conveyor.
2. Description of the Prior Art
Racks or shelvings for articles are known having a horizontal row of mutually parallel supply tracks which discharge out onto a common conveyor and in which there is utilized a remotely controlled article stopping mechanism for each supply track. With such racks or shelvings, there is utilised a separate conveyor for each horizontal row of supply tracks, the conveyors being arranged at elevations above each other corresponding to the horizontal rows of supply tracks. Such known racks for articles of commerce or merchandise having conveyors arranged above each other, involve several disadvantages and limitations.
The conveyors arranged above each other will, necessarily, take up a substantial portion of the area endways outside the supply tracks so that it is difficult to achieve full employment of the volume of the rack in the height direction.
By employing a common conveyor for each horizontal row of supply tracks, where the supply tracks discharge directly out onto the conveyor, there is a demand for a special control of the supply tracks with a view to avoiding collisions between an article which strays on the conveyor and an article which is to be transferred from the supply track to the conveyor and blocking of the supply tracks or undesired accumulation of the articles on the conveyor. Special control must also be provided for, in order to ensure that the different articles are supplied in a definite sequence on the conveyor, independently of the mutual disposition of the articles in the rack. It is difficult to combine such requirements and needs with a rapid and accurate handling of the articles.
By employing a separately controlled article-stopping mechanism for each individual supply track, there results a complicated set-up of control mechanisms with a corresponding greater danger for malfunctioning or other failure in the control mechanisms.
U.S. Pat. No. 3,674,159 (Lemelson) discloses a warehousing system comprising a storage rack for storing loads thereon and a stacker crane moveable alongside the rack for depositing loads into and removing loads from selected storage locations in the storage rack. However, such a system is only concerned with transferring a load from the storage rack to a storage position on the stacker crane and not with conveying the load from that storage position to a delivery location. Apparently, the loads must be transported individually or in groups by way of the stacker crane, a rather awkward and time-consuming operation.
U.S. Pat. Nos. 3,528,566 (Weir) and 3,447,699 (Weir) certainly disclose conveying articles to a delivery location in a relatively simple manner but the withdrawal from the storage rack is performed manually. The operator must move the article outwardly from the rack and inwardly onto a transfer table from which it is shifted further inwards onto an inclined conveyor. In as much as the adjustment of the height of the article retrieving device is effected by manual control, this does not present a problem.